Cooling means

ABSTRACT

The present invention comprises a means for cooling an engine, such as might be found in a conventional automotive vehicle. More particularly, the instant invention comprises: (1) a heat pipe having a condenser end and an evaporator end, wherein the evaporator end is in thermal contact with the engine to be cooled; and (2) a finned heat sink joined to the condenser end, whereby heat from said engine is vaporously transported through said heat pipe from the evaporator end to the condenser end of said pipe, and convected therefrom into the ambient air.

United States Patent Pessolano et a1.

1 1 COOLING MEANS 3273,23

, 3,33 [75] Inventors: Richard L. Pessolano, Sparta; Robin 3 701342 1 B. Rhodes, Parsippany, both of NJ. 3731660 [73] Assignee: Isothermics, Inc., Augusta, NJ.

[22] Filed: July 23, 1973 [21] Appl. No.: 382,024

1 [52] US. Cl 165/51; 33/1267 R; 73/346; 184/622; 184/104 B; 165/105 [51] Int. Cl. ..F01p 3/12 [58] Field of Search 165/105, 51; 184/622, 184/104 B; 33/1267 R, 126.7 A; 73/344, 346

[56] References Cited UNITED STATES PATENTS 837,499 12/1906 Perkins et aL 165/105 2,487,215 11/1949 Blatt 184/104 B 2,629,041 2/1953 184/104 A X 2,766,974 10/1956 McCnne1l 165/105 X 2,835,480 /1958 Perez 165/105 X May 20, 1975 Bolles 33/1267 R McDougal Owsley et a1. /105 X Leffert 165/105 X Primary Examiner-Albert W. Davis, Jr. Attorney, Agent, or Firm-Mel K. Silverman, Esq.

ABSTRACT The present invention comprises a means for cooling an engine, such as might be found in a conventional automotive vehicle. More particularly, the instant invention comprises: (1) a heat pipe having a condenser end and an evaporator end, wherein the evaporator end is in thermal contact with the engine to be cooled; and (2) a finned heat sink joined to the condenser end, whereby heat from said engine is vaporously transported through said heat pipe from the evaporator end to the condenser end of said pipe, and convected therefrom into the ambient air.

5 Claims, 2 Drawing Figures PATENTEU HAYZO I975 l COOLING MEANS BACKGROUND OF INVENTION The present invention relates to a novel application of heat pipe technology.

A heat pipe can be best described as a miniaturized, hermetically sealed evaporating and condensing system. The function of a heat pipe is to effect an axial transfer of thermal energy.

A heat pipe consists essentially of a sealed elongated container, a capillary wick structure which is circumferentially secured to the interior surface of the 'container, and a quantity of working fluid sufficient to at least partially saturate the wick structure. After the working fluid has been added to the system, the container is sealed while under a vacuum.

Because the container is sealed under a vacuum, the working fluid is in equilibrium with its own vapor, Thus, any application of heat to any external surface of the pipe will cause an instantaneous evaporation of the working fluid near the heated surface. In the evaporation process, the latent heat of vaporization is absorbed by the vapor. Latent heat is the ratio of (a) the heat absorbed during a change of phase, e.g., from liquid to vapor, to (b) the mass of the system undergoing the change of phase, I

The vapor generated as a result of a heat addition creates a pressure gradient within the heat pipe which forces the vapor to an area of the ,heat pipe having a lower pressure and temperature. The lower temperature causes condensation of the vapor, thereby allowing the latent heat of vaporization to be dissipated into the condenser surfaces of the heat pipe. Heat may be removed from the condenser surfaces by conduction, convection, or radiation into the surrounding environment.

After evaporation, the condensed working fluid is returned to the evaporator region (area of heat addition) by capillary pumping forces within the circumferential interior wick structure.'This return may occur either with or without the aid of gravity.

There are, as aforestated, only three basic components to any heat pipe: the container, the wick, and the fluid. This extreme simplicity, taken in complement with the fact of the absence of any moving mechanical parts, has of late caused the heating and refrigeration A industries to pay particular attention to heat pipe technology. An additional reason for such attention is the high efficiency of operation which the heat pipe enjoys. Such efficiency derives from the fact that the quantity of heat absorbed in the vaporization of a fluid is enormous compared to that absorbed during an increase of temperature of a liquid fluid. For example, the amount of heat absorbed by one pound of water while being heated from 160 F to 161 F is l BTU. However, if the same pound of water were to be first vaporized at 160 F, and then heated to 161 F, the amount of heat absorbed would be 1,000 BTU. Hence, the same one pound mass of water can offer 1,000 times the heat transfer capability over the same temperature increment when the latent heat of vaporization is utilized, as in heat pipe technology.

SUMMARY OF THE INVENTION The present invention constitutes a new use of certain areas of heat pipe technology, and its application to a particular need which exists in the automotive industry. More particularly, a long existent problem in auto engine operation has been that of maintaining the oil, or other lubricating fluid, at a sufficiently low temperature in order to prevent the engine and other operative components of the automotive vehicle from overheating. This problem is particularly common when the vehicle must operate in a relatively hot climatic environment as well as in situations wherein the vehicle is required to haul a relatively heavy load. The latter problem is often the case where automobiles are used to pull trailers and where tractor trailers are required to pull container loads in excess of their normal capacity.

Accordingly, it can be readily appreciated that the operation of a wide variety of vehicles would be enhanced if their cooling liquid (in most cases water, and- /or their lubricating liquid, e.g., oil) could be kept at a lower temperature than is now practicable to achieve.

In addition, it' is possible to remove heat directly at the point of generation, that is, from the cylinder walls and the bearing supports, and thus to maintain the engine within an acceptable temperature range.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a cross sectional schematic view of one embodiment of the present invention.

FIG. 2 is a view of the present invention utilized in association with the engine block of an automobile.

DETAILED DESCRIPTION OF THE INVENTION Turning to FIG. 1, there is illustrated a heat pipe 10 having an evaporator end 12 and a condenser end 14. Joined to the condenser end is heat sink 16.

The general exterior shape of the present cooling means is, in one embodiment, adapted such that it may readily replace the standard dip stick, or any equivalent thereof, on a motor vehicle such as a car, truck or motorcycle. In addition, and as will be shown, thecooling means further functions as an oil level indicator, as does the original-equipment dip stick, and may also function as an oil temperature indicator.

The length and diameter of the heat pipe 10 that is utilized is determined by the allowable clearances within the crank case of the motor vehicle. The size and geometry of the heat sink 16 is determined by heat transfer considerations, which will vary somewhat depending on the particular motor vehicle to'which'one may desire to adapt the present cooling means. Also, manufacturing and aesthetic factors may be considered inthe design of the heat sink. i

The heat transfer mechanisms involved in the present cooling means are as follows: First, convection occurs from the oil 18 (within the motor vehicle) to the exterior surface 20 of the evaporator end 12 of the cooling means. This process is followed by conduction through heat pipe wall 22 and by evaporation of working fluid 24 within the heat pipe. Said evaporation will result in the transport of heat-carrying vapor to the condenser end 14 of the heat pipe. At the condenser end the vapor will condense, giving up its latent heat of vaporization. This heat is conducted through the condenser portion of the heat wall, through an interface 25 between the heat pipe 14 and the heat sink 16 (if and where such an interface exists in any given design), and finally conducted through the heat sink 16 to the surface thereof, from which point convection into the ambient air oc-, curs as the final heat transfer mechanism involved.

After condensation, the condensed working fluid will return within a circumferential capillary pumping channel 26 which is circumferentially secured to the interior surface of the heat pipe. The above processes of: (1) heat transfer from the hot oil bath to the working fluid 24, (2) evaporation of said working fluid and the vaporous transfer therein of heat from the oil, axially upward to the condenser end where said heat is discharged into the ambient air, and (3) the return of the condensed working fluid within said circumferential capillary pumping channel, are repeated continuously and indefinitely until the oil 18 falls to a temperature that will not cause further evaporation of the working fluid 24.

Because of the general orientation of dipsticks in motor vehicles, i.e., that of between vertical and 45 from vertical, most applications of the present invention will be such that the heat sink portion 16 is above the end 12 (that is immersed in the oil 18.), thus gravity aids in the condensate return 26 within the heat pipe. This means that the role of the wick structure in the present heat pipe application is of less importance than in other heat pipe applications. Accordingly, it would be possible to construct a workable cooling means of the present type without the use of a wick structure. Such a design is often termed a reflux condenser. It is, however, to be noted that the efficiency of operation of such a reflux condenser would undoubtedly be inferior to that of the first above-discussed embodiment.

Because of the relatively poor heat transfer characteristics of most motor oils, the surface area of the evaporator end 12 demands particular attention in the heat transfer process. In order to solve this problem, it is desirable to obtain an evaporator configuration which will possess the greatest possible surface area 20. Such an objective may be obtained by forming the area 20 in a finned arrangement. For example, the end 12 of the pipe may have (a) either radial or axial fins, (b) grooves, or (c) a threaded design, in order to increase the effective heat transfer area 20 as well as to aid in the creation of capillary forces which will assist the condensate return within the capillary structure 26.

The heat sink 16 like the evaporator surface 20, requires a surface area of maximum surface dimension. Accordingly, a configuration such as a plurality of fins will be suitable for most applications. The heat sink may be manufactured as a separate part which is later joined to the end 14 by welding, brazing, sodering, epoxy bonding, shrink fit, or any other practical means ofjoining. In the alternative, the heat sink may be manufactured as an integral part of the present cooling means. In either case, the heat sink may be formed as a machine part, a casting part, an extrusion, a weldment, or any other form suitable to a finned surface.

An alternate design might employ a heat pipe with its evaporator section rigidly affixed to or near a heat producing portion of the engine such as the cylinder walls or the bearing supports. In such a design the primary mechanism of heat transfer to the heat pipe would be that of conduction from the hot surrounding metal. The condenser of the heat pipe might be disposed into a flow of engine coolant, or might protrude from the engine and extend into a cooling ambient air stream.

The heat pipe working fluid 24 will be chosen on the basis of the needs of the particular application: for example, the heat transfer capability of the fluid will be considered as will the boiling point of the fluid and its molecular integrity. A heat pipe can be obtained that will function only when the temperature of the oil 18 exceeds a given temperature.

It is also to be noted that the present cooling means may serve as an oil temperature indicator. Such a function may be readily achieved by equipping the heat pipe with a bi-metallic thermal element having an indicating dial and pointer. Said bi-metallic element can readily be incorporated into the heat pipe structure of FIG. 1.

By the provision of a fill line 28 the present cooling means can also be utilized as an oil level indicator, in similar fashion to a conventional dip stick.

The exterior of the cooling means may be protected by any suitable surfacing, for example, a copper shell, affixed immediately about the heat pipe, in conjunction with a nickel plate coating about said copper shell.

Turning now to FIG. 2, we can see another important application of the present invention. FIG. 2 illustrates, in break-away view, an engine block 30 that has been adapted for use with the present cooling means. Element 32 is a water jacket; element 34 is a bearing housing; and element 36 is a crankshaft channel.

The present cooling means is inserted into the bearing housing 34. It is to be noted that said insertion represents merely one mode of juxtaposing the cooling means to a heat source within the engine. It is to be noted that the heat sink 16 may be divided, as is shown in FIG. 2, so as to permit heat to be vaporously transported into either of two regions. There are a virtually infinite number of modes that might be suitable or indicated in any given application. Also, it is noted that engines other than auto engines could be adapted for use with the present invention.

It is thus seen that the object of obtaining an improved cooling means for a subsystem of an automotive vehicle has been efficiently attained by the abovedescribed embodiments of the present invention. While there have been herein shown and described the preferred embodiments of the presentinvention, it will be understood that the invention may be embodied otherwise than as herein specifically illustrated or described and that within said embodiments certain changes in the detail and construction, and the form of arrangement of the parts may be made without departing from the underlying idea of principles of this invention within the scope of the appended claims.

Having thus described our invention, what we claim as new useful and non-obvious, and accordingly secure by Letters Patent of the United States is:

1. A means for cooling an oil lubrication subsystem of an automotive vehicle, comprising:

a. a heat pipe having a condensor end and an evaporator end, said evaporator end removably insertable into the dip stick hole of the oil lubrication subsystem, said heat pipe including an oil level indicator placed near said evaporator end; and

b. a heat sink joined to the condensor end, whereby heat from said subsystem is vaporously transported within said heat pipe from the evaporator end to the condensor end, and transported therefrom into a medium of lower temperature than that of said subsystem.

2. The cooling means as recited in claim 1 in which said heat sink is finned.

3. The cooling means as recited in claim 1 in which said evaporator end is finned.

6 heat pipe into the dip stick hole of said subsystem, whereby heat from said subsystem is vaporously transported within said heat pipe from its evaporator end to its condensor end, and transported therefrom into a medium of lower temperature than that of said subsystem. 

1. A means for cooling an oil lubrication subsystem of an automotive vehicle, comprising: a. a heat pipe having a condensor end and an evaporator end, said evaporator end removably insertable into the dip stick hole of the oil lubrication subsystem, said heat pipe including an oil level indicator placed near said evaporator end; and b. a heat sink joined to the condensor end, whereby heat from said subsystem is vaporously transported within said heat pipe from the evaporator end to the condensor end, and transported therefrom into a medium of lower temperature than that of said subsystem.
 2. The cooling means as recited in claim 1 in which said heat sink is finned.
 3. The cooling means as recited in claim 1 in which said evaporator end is finned.
 4. The cooling means as recited in claim 1 in which said heat pipe comprises a reflux condenser.
 5. A new use of a heat pipe, wherein said new use resides in a method of cooling an oil lubrication subsystem of an engine, comprising the steps of: a. adjoining a heat sink to the condensor end of the heat pipe; and b. removably inserting the evaporator end of said heat pipe into the dip stick hole of said subsystem, whereby heat from said subsystem is vaporously transported within said heat pipe from its evaporator end to its condensor end, and transported therefrom into a medium of lower temperature than that of said subsystem. 